Coarse fraction, radiocarbon datings, and planktic stable isotope data from sediment core PS93/031-5 (NW Fram Strait)

The coarse fraction content and the oxygen and carbon isotopic compositions of two morphotyes of planktic foraminifers Neogloboquadrina pachyderma were determined from sediment samples obtained from sediment core PS93/031-5. The age model is based on 9 radiocarbon datings obtained on ~2000 specimens of N. pachyderma each. Grain size measurements occurred in May-July 2017. Stable isotope measurements were performed in August 2018 to February 2019. Radiocarbon datings were performed in August 2018 to April 2019. According to the radiocarbon datings (no reservoir correction applied) the sediment core covers the Late Quaternary time interval from 4,023 to 18,135 years before present (1950 CE). No sediments are present from the interval 11,170-15,950 years before present (hiatus at 25 cm core depth). When a conversion to calibrated years is performed with the program Calib 8.2 (http://calib.org/calib/), using the IntCal20 data set and applying a reservoir correction of 550 years, the core covers the interval of 3,750-23,230 years before present, with the hiatus covering the interval 12,660-18,550 years. Sediment core PS93/031-5 was obtained during RV POLARSTERN expedition PS93.1 in the northwestern Fram Strait on the Northeast Greenland continental margin from 2,135 m water depth. The data were collected to reconstruct the Late Quaternary paleoenvironment in the northwestern Fram Strait, the glacial history of the northeast Greenland shelf, and the export of freshwater from the Arctic to the North Atlantic in the last ca. 21,000 years. Sediment slices of approx. 5 mm thickness were taken from sediment core PS93/031-5 every 0.5 cm (~30 g dry sediment per sample). Sediments were freeze-dried, weighed, and washed with deionized water through a 63 µm mesh. The remaining coarse fraction was dried at 50°C and weighed. Coarse fraction percentages were calculated as [coarse fraction weight] * 100 / [dry bulk weight]. Planktic foraminifers Neogloboquadrina pachyderma were hand-picked from the 100-250 µm fraction for stable isotope measurements. 25 specimens of morphotypes 1 and 2 as well as 40 specimens of morphotypes 4 and 5 (following the morphotype concept of Eynaud, 2011) were analyzed separately for stable oxygen and carbon isotope compositions (δ18O, δ13C) in the stable isotope lab of AWI on a Finnigan MAT 253 gas mass spectrometer coupled to the automatic carbonate preparation device Kiel IV. The mass spectrometer was calibrated via international standard NBS19 to the PDB scale. Results are given in δ-notation vs. VPDB. Details on ice volume effect corrections and calculations of differences to oxygen isotope values of equilibrium calcite (δ18Oec) are given in Spielhagen and Mackensen (under review). Radiocarbon datings were performed on ~2,000 specimens of N. pachyderma (morphotype 1-2) at the at the AMS-14C facility of the Leibniz Laboratory for Age Determination and Isotope Research of Kiel University.